How To Test For Vitamin C

This article will explain how to test for vitamin C. A popular science project is testing for the vitamin C content in fruit juices because there is little available information. At the end of your experiment you will know which fruit juices contain the most vitamin C. Vitamin C is very important to our health. It acts as an antioxidant, strengthens muscles and blood vessels, important in lowering blood pressure, prevents spasms of arteries that could lead to heart attacks, helps wounds heal, fight viruses, lowers the risk of getting cataracts, reduces the activity of the enzyme responsible for deteriorating the eyes, kidneys and nerves in people with diabetes, protects the body against toxic minerals, prevents scurvy, and reduces reoccurring boils.

For this experiment you will need the following:

  • 2% iodine solution
  • cornstarch
  • water
  • 15 ml test tubes
  • samples of a variety of juices


  1. In a pot, make a paste out of one tablespoon of cornstarch and water.
  2. Add 250 ml of water and let it boil for five minutes.
  3. Use an eyedropper and add 10 drops of this boiled solution to 75 ml of water.
  4. Add iodine until the mixture turns dark purple-blue color (your indicator solution).
  5. For every product you want to test you will place 5 ml of the indicator solution in a separate 15 ml test tube.
  6. Get a clean eyedropper and fill with approximately 10 drops of juice. (If you are using fruit, use a blender to extract juice from the fruit, then strain.) Counting the drops, slowly add your first sample to the first test tube. Count how many drops it takes for the mixture to turn clear. Repeat this procedure for each juice or fruit you are testing and keep track of how many drops you used before the mixture became clear. Be sure to use a clean eyedropper for each item you are testing.
  7. By comparing the amount of drops you use to turn the solution clear, you will be able to determine which samples had the most vitamin C content. If it does not change to a clear liquid, it does not have much vitamin C content.

Results will vary when using canned juice, fresh juice, or juice concentrate. There are six main factors that may affect the levels of vitamin C:

  • climate and production (e.g. temperature and fertilizers)
  • maturity of fruit and location on the tree (e.g. exposure to sunlight)
  • type of fruit
  • parameters for processing (fresh, canned, concentrate)
  • container (cans, glass, cardboard cartons)
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